I used Dexamethasone because I had it available to me for self diagnosis. I took it for 4 months then tapered off in 6 months. I did not use anything else. Dex is similar to prednisone just a stronger version. So 2mg of dex is 10mg of prednisone. (roughly). If it were me, your already on prednisone. I dont know any of your particulars but I would try to taper off without more drugs. Either of the other two can take up 8 weeks to start working. I was only dealing with PMR. No other autoimmune. You are right at the taper wall on 5 mg. It will get harder from here but go real slow and try to wean off. If you you do take the others they may help some at this point and then stop. They usually like you stay on them for up to year after prednisone just to make sure the PMR is gone and your cortisol has restarted.